The present invention relates to an electrohydraulic control unit for rotor blade adjustment of a wind farm.
One such electrohydraulic control unit is known from German Utility Model DE 203 17 749. In wind farms, rotor blades are adjustable about a rotor blade axis within a predetermined angle range, so that the rotor blade can be positioned into the wind (known as “pitching out”) or positioned relative to the wind direction (known as “pitching in”). Since rotor blades are very expensive and vulnerable, and because of the strong forces that prevail especially in a strong wind, a rotor blade adjustment must be made sensitively and without abrupt deceleration or acceleration.
The rotor blade adjustment is done hydraulically via a hydraulic cylinder, with one piston chamber and one piston rod chamber. A pressure line is in constant pressure fluid connection with the piston rod chamber. The piston rod chamber communicates with the piston chamber via a proportional seat valve. The piston chamber can be relieved to a tank via a further proportional seat valve. In this embodiment, if the high degree of fail-safety is to be attained, the additional valves required entail major effort and expense for equipment, and hence complex engineering and high costs.